The present invention relates to a method and apparatus for measuring the flash duration of a flash unit.
The flash duration of flash units can be defined in various ways. Best suited for estimating the anticipated sharpness or focus of a moving object is the so-called total flash duration t 0.1, the so-called tenth estimation. This time interval is measured from that point in time at which the momentary light intensity has exceeded 10% of its maximum. The end point is obtained when the momentary light intensity has again dropped below this value. With the aid of an intensity/flash duration curve, the flash duration can be easily determined; however, it is not practical to measure this flash duration. This is so because if one wishes to measure the flash duration, the problem exists that in the rising leg of the flash curve, one does not yet know how high the maximum of the light intensity will be. For this reason, the beginning of the desired flash duration can also not be fixed. On the other hand, if the maximum of the light intensity is exceeded, although one then knows the maximum value and also knows at what point in time the beginning of the measurement should have been effected, at this point in time the rising leg of the intensity/flash duration curve is no longer available.
It is therefore an object of the present invention to provide a method and apparatus with which for the first time the flash duration itself can be measured.